A shock tube is a facility that produces fast and A relatively high temperature flows by driving a strong shock wave into quiescent gas. From simple shock tube theory it is possible to show that in order to obtain high Mach number primary shock waves one should employ a very light driving gas at the highest pressure and temperature possible. These conditions are most commonly met by the explosion of a stochiometric mixture of inflammable gases, such as oxygen and hydrogen diluted with helium.

British trade unions were the first to protect the interests of working people because it was Britain that had pioneered industrial development. Most unions were based primarily on craft to begin with. They were an extension of the old guild system, and entrance into them required a long apprenticeship but conferred considerable benefits in terms of security and status. Many of them had complicated and often idealistic constitutions such as the Engineers Union with its democratic checks and balances based on the philosophy of Rousseau. In fact these early unions were designed as much to protect the workers in them against other workers as to take on the role of social organisations resisting unfair employers.

The large unions for manual workers came later as more and more working class people abandoned the land and fled to the factories. These unions were more embracing, less concerned about qualification and often survive today with essentially the same constitution and rule books of their original founders. The main role of these unions quickly became the alleviation of the lot of working people at a time when the worst type of industrial boss practised the survival of the fittest, while often the weak went to the wall.

Most regional airports are grateful for the flexibility of the approach in the White Paper, but I feel that some more positive guidance ought to be given in some cases. Many airports are still very uncertain of their future. The importance of this longer term planning is very relevant because people in authority have got to make their minds up; some airports have to decide whether to exist or to go under, and they can only make that decision on what happens after 1990. There is a certain freedom of choice obviously left to airport operators and airlines, and one question which we have to ask is, will new services be allowed into regional airports, outside the Government's policy, if both the airport and the airline feels it is going to be a viable service? I think a great deal of care is needed to ensure that any such move of that sort does not undermine the basic airports policy and dilute its effectiveness.

There are two methodological approaches by which airline efficiency might be measured. One way is by using the concept of comparative airline efficiency. Using this concept, efficiency is measured with respect to typical, mean, or expected industrial average performances. The approach adopted in this paper is to measure airline efficiency by using the concept of monitored airline performances. In this kind of exercise efficiency is measured with respect to the airline's stated objectives. In using the. monitoring approach a consideration of general airline objectives is required. Typical airline objectives are discussed below, as are the expected repercussions on efficiency parameters. After discussing objectives in general, British Airways’ corporate objectives will be discussed in particular. Finally, whether British Airways has been successful or not in reaching its objectives will be investigated. But as a prerequisite to this investigation some discussion will be necessary of the most appropriate indicators to use for monitoring the objectives.

A stiffened shear web, consisting of a thin plate (referred to simply as the web) attached to longitudinal members (or flanges) and supported by a series of transverse stiffeners, buckles in a mode involving both the web and stiffeners, at a shear stress which also depends on the restraint between the web and flanges. With increasing stiffener size changes in the mode of buckling occur until, at a certain critical value of the flexural stiffness of the stiffener, buckling is largely confined to the web between stiffeners, and the buckling coefficient is then practically constant. The buckling coefficient reduces to that of an unstiffened flat plate with decreasing stiffener size.

Engineering Sciences Data Item 02.03.02 plots buckling coefficients for long shear webs with uniform, equally-spaced stiffeners. The curves are based on work by Stein and Fralich, for stiffeners of zero torsional rigidity and simply-supported longitudinal edges, and on a more recent series of papers by Cook and Rockey (listed in the Data Item) which extend the analysis to clamped, as well as simply-supported, webs and also include the torsional rigidity of the stiffeners.

The demand for aerial spraying is determined by agricultural needs and timing. The degree to which an aerially applied compound is effective is governed by many factors, which exercise their influence both at the time the compound is applied and for some time before and after this event. The impact of the weather and its interaction with other factors may be felt at all stages of relevance to an aerial spraying operation—these stages, which are of course also relevant to ground based spraying operations, may be categorised as follows:

• (i) The long term pre-spraying environment (measured on a time scale of days or weeks).

• (ii) The immediate pre-spraying environment (measured on a time scale of hours).

• (iii) Conditions at the time of spraying.

• (iv) The immediate post-spraying environment.

• (v) The long term post-spraying environment.

The title ‘The Community Response’ sums up very aptly, if inadvertently, the place of the community as the Government sees it in the formulation of airport strategy. In other words, to respond rather than to participate; a sort of reluctant anchor that has to be dragged along in response to proposals made by others. Airports should be planned to serve the Community; that is their function. They do not exist merely to facilitate the landing and take-off of passengers and freight in a vacuum unrelated to the locality in which they are sited. People who use airports have an involvement with the community whether it be through business, tourist or domestic connections.

The GLC has consistently recognised the importance of London's airports, especially Heathrow, to the economic well being of London and the South East. With the abandonment of Maplin we have accepted that at least for the time being, the increased demand for airport capacity in the South East will have to be met by some expansion at existing airports, but we have a wider duty also to ensure that the social planning and environmental aspects linked with airport developments are taken into account.

Most spacecraft attitude control systems employing mass-expulsion techniques use some form of pulse modulation at the output from the control system to the gas control valves. In a number of early designs such modulation was introduced almost accidentally by surrounding simple relay-type switching logic with a feedback loop containing a first-order lag to provide ‘derived rate’ damping. This arrangement gives pulse width and pulse frequency modulation (Combined pulse modulation).

Such a modulation scheme was devised by Schaefer in 1962 which he called a Pulse Ratio Modulator (PRM). His main concern was the mechanisation of the quasistatic equations of the modulator and he did not investigate the stability of systems containing a PRM.

Future air transportation growth will be limited not only by the availability of personal disposable income for travel and by the maximum reasonable needs of business travellers, but also by competition from other modes such as the automobile, train, exotic guided ground transportation systems, such as magnetically levitated vehicles, buses and ships. Because of the aircraft's overwhelmingly superior speed and cost characteristics with respect to passenger ships, the passenger ship has been largely reduced to a recreational facility rather than a transportation mode. There are, of course, a few exceptions for short voyages between origins and destinations separated by water. But it is sufficiently clear that water transportation will not compete economically with air, except at very short ranges in a few unique situations, so that this mode will not be discussed.

Calculations of the aerodynamic loads on wings in atmospheric gusts are an essential part of aircraft design for three main reasons. Firstly, an estimate of the gust loads which the aircraft must withstand is an important element of the structural design calculations in terms of ensuring both static load bearing capability and an adequate fatigue life. Secondly, the calculated gust loads provide the input to a suitable mathematical model of the aircraft structure in order to arrive at an assessment of aircraft accelerations and ride behaviour in expected levels of atmospheric turbulence. This is particularly significant for high speed military aircraft operating at low altitudes. Thirdly, aerodynamic loads due to gusts can be viewed as perturbing influences to aircraft stability so that the performance of an active control, gust alleviation or ride control system has to be considered with a detailed knowledge of the time variance of aerodynamic gust loads in mind.